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目的 比较正常新生儿和健康成人免疫球蛋白重链可变区 (IgH)基因的可变区基因片段 (VH)、多样化基因片段 (D)和连接区基因片段 (JH)的使用 ,VH 上的突变 ,N区 -D基因片段 -N区 (NDN)长度以及开放性阅读框 (ORF)等情况 ,探讨新生儿IgH重排基因特征及其多样性。 方法 10例正常足月新生儿脐血和 8例健康成人外周血DNA被抽提 ,IgH基因被扩增、克隆和测序。结果 ①对于VH 和D的使用 ,新生儿和成人相似 ,即VH3使用率最高、VH7使用率最低 ,D2被优先使用 ;而对于JH 的使用 ,新生儿和成人不同 ,即新生儿偏倚使用JH3 ,成人使用JH 则趋向随机化。②新生儿和成人IgH重排基因的VH-D -JH 连接点处均有N区插入 ,但新生儿的NDN长度 [(2 1.2± 5 .7)bp]短于成人 [(2 6 .6± 6 .5 )bp]。③新生儿的IgH基因序列无碱基缺失而成人存在 ;新生儿IgH基因少有体突变 (2 9.2 % ) ,而 77.1%的成人IgH基因存在体突变。④新生儿有ORF的IgH基因序列为91.7% ,而成人为 10 0 %。结论 正常新生儿和健康成人的IgH重排基因序列存在着异型性。新生儿的IgH重排基因已处于活化状态 ,但由于VH,D和JH 的偏倚使用 ,NDN短以及少有突变 ,其多样性有限。
OBJECTIVE: To compare the use of the variable region gene fragment (VH), the diversified gene fragment (D) and the junctional region gene fragment (JH) of immunoglobulin heavy chain variable region (IgH) genes in normal newborns and healthy adults, (NDN) length and open reading frame (ORF) of N region, to explore the characteristics and diversity of IgH rearrangement gene in neonates. Methods 10 cases of normal full-term neonatal umbilical cord blood and 8 cases of healthy adult peripheral blood DNA was extracted, IgH gene was amplified, cloned and sequenced. Results ① For both VH and D, newborns and adults were similar, with the highest VH3 usage and the lowest VH7 usage, with D2 preferentially used; whereas for JH, newborns and adults differed from each other in that newborns were biased with JH3, JH tends to be randomized in adults. Neonatal and adult IgH rearrangement gene VH-D-JH junction at both N-region insertion, but the NDN length of neonates [(2 1.2 ± 5 .7) bp] shorter than adults [(26.6 ± 6 .5) bp]. (3) The IgH gene sequence of newborns is absent in adults and exists in adults; IgH gene of newborn has few somatic mutation (2 9.2%), while 77.1% of adult IgH gene exists in vivo mutation. ④ Newborns with ORF IgH gene sequence was 91.7%, while adults were 10%. Conclusion The IgH rearrangement gene sequence of normal newborn and healthy adult has atypia. Neonatal IgH rearrangement genes are already activated, but their diversity is limited due to the biased use of VH, D and JH, short NDNs and few mutations.